drivers/staging/zram/zram_drv.c

   1 /*
   2  * Compressed RAM block device
   3  *
   4  * Copyright (C) 2008, 2009, 2010  Nitin Gupta
   5  *
   6  * This code is released using a dual license strategy: BSD/GPL
   7  * You can choose the licence that better fits your requirements.
   8  *
   9  * Released under the terms of 3-clause BSD License
  10  * Released under the terms of GNU General Public License Version 2.0
  11  *
  12  * Project home: http://compcache.googlecode.com
  13  */
  14
  15 #define KMSG_COMPONENT "zram"
  16 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  17
  18 #include <linux/module.h>
  19 #include <linux/kernel.h>
  20 #include <linux/bio.h>
  21 #include <linux/bitops.h>
  22 #include <linux/blkdev.h>
  23 #include <linux/buffer_head.h>
  24 #include <linux/device.h>
  25 #include <linux/genhd.h>
  26 #include <linux/highmem.h>
  27 #include <linux/slab.h>
  28 #include <linux/lzo.h>
  29 #include <linux/string.h>
  30 #include <linux/vmalloc.h>
  31
  32 #include "zram_drv.h"
  33
  34 /* Globals */
  35 static int zram_major;
  36 struct zram *devices;
  37
  38 /* Module params (documentation at end) */
  39 unsigned int num_devices;
  40
  41 static void zram_stat_inc(u32 *v)
  42 {
  43         *v = *v + 1;
  44 }
  45
  46 static void zram_stat_dec(u32 *v)
  47 {
  48         *v = *v - 1;
  49 }
  50
  51 static void zram_stat64_add(struct zram *zram, u64 *v, u64 inc)
  52 {
  53         spin_lock(&zram->stat64_lock);
  54         *v = *v + inc;
  55         spin_unlock(&zram->stat64_lock);
  56 }
  57
  58 static void zram_stat64_sub(struct zram *zram, u64 *v, u64 dec)
  59 {
  60         spin_lock(&zram->stat64_lock);
  61         *v = *v - dec;
  62         spin_unlock(&zram->stat64_lock);
  63 }
  64
  65 static void zram_stat64_inc(struct zram *zram, u64 *v)
  66 {
  67         zram_stat64_add(zram, v, 1);
  68 }
  69
  70 static int zram_test_flag(struct zram *zram, u32 index,
  71                         enum zram_pageflags flag)
  72 {
  73         return zram->table[index].flags & BIT(flag);
  74 }
  75
  76 static void zram_set_flag(struct zram *zram, u32 index,
  77                         enum zram_pageflags flag)
  78 {
  79         zram->table[index].flags |= BIT(flag);
  80 }
  81
  82 static void zram_clear_flag(struct zram *zram, u32 index,
  83                         enum zram_pageflags flag)
  84 {
  85         zram->table[index].flags &= ~BIT(flag);
  86 }
  87
  88 static int page_zero_filled(void *ptr)
  89 {
  90         unsigned int pos;
  91         unsigned long *page;
  92
  93         page = (unsigned long *)ptr;
  94
  95         for (pos = 0; pos != PAGE_SIZE / sizeof(*page); pos++) {
  96                 if (page[pos])
  97                         return 0;
  98         }
  99
 100         return 1;
 101 }
 102
 103 static void zram_set_disksize(struct zram *zram, size_t totalram_bytes)
 104 {
 105         if (!zram->disksize) {
 106                 pr_info(
 107                 "disk size not provided. You can use disksize_kb module "
 108                 "param to specify size.\nUsing default: (%u%% of RAM).\n",
 109                 default_disksize_perc_ram
 110                 );
 111                 zram->disksize = default_disksize_perc_ram *
 112                                         (totalram_bytes / 100);
 113         }
 114
 115         if (zram->disksize > 2 * (totalram_bytes)) {
 116                 pr_info(
 117                 "There is little point creating a zram of greater than "
 118                 "twice the size of memory since we expect a 2:1 compression "
 119                 "ratio. Note that zram uses about 0.1%% of the size of "
 120                 "the disk when not in use so a huge zram is "
 121                 "wasteful.\n"
 122                 "\tMemory Size: %zu kB\n"
 123                 "\tSize you selected: %llu kB\n"
 124                 "Continuing anyway ...\n",
 125                 totalram_bytes >> 10, zram->disksize
 126                 );
 127         }
 128
 129         zram->disksize &= PAGE_MASK;
 130 }
 131
 132 static void zram_free_page(struct zram *zram, size_t index)
 133 {
 134         u32 clen;
 135         void *obj;
 136
 137         struct page *page = zram->table[index].page;
 138         u32 offset = zram->table[index].offset;
 139
 140         if (unlikely(!page)) {
 141                 /*
 142                  * No memory is allocated for zero filled pages.
 143                  * Simply clear zero page flag.
 144                  */
 145                 if (zram_test_flag(zram, index, ZRAM_ZERO)) {
 146                         zram_clear_flag(zram, index, ZRAM_ZERO);
 147                         zram_stat_dec(&zram->stats.pages_zero);
 148                 }
 149                 return;
 150         }
 151
 152         if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
 153                 clen = PAGE_SIZE;
 154                 __free_page(page);
 155                 zram_clear_flag(zram, index, ZRAM_UNCOMPRESSED);
 156                 zram_stat_dec(&zram->stats.pages_expand);
 157                 goto out;
 158         }
 159
 160         obj = kmap_atomic(page, KM_USER0) + offset;
 161         clen = xv_get_object_size(obj) - sizeof(struct zobj_header);
 162         kunmap_atomic(obj, KM_USER0);
 163
 164         xv_free(zram->mem_pool, page, offset);
 165         if (clen <= PAGE_SIZE / 2)
 166                 zram_stat_dec(&zram->stats.good_compress);
 167
 168 out:
 169         zram_stat64_sub(zram, &zram->stats.compr_size, clen);
 170         zram_stat_dec(&zram->stats.pages_stored);
 171
 172         zram->table[index].page = NULL;
 173         zram->table[index].offset = 0;
 174 }
 175
 176 static void handle_zero_page(struct page *page)
 177 {
 178         void *user_mem;
 179
 180         user_mem = kmap_atomic(page, KM_USER0);
 181         memset(user_mem, 0, PAGE_SIZE);
 182         kunmap_atomic(user_mem, KM_USER0);
 183
 184         flush_dcache_page(page);
 185 }
 186
 187 static void handle_uncompressed_page(struct zram *zram,
 188                                 struct page *page, u32 index)
 189 {
 190         unsigned char *user_mem, *cmem;
 191
 192         user_mem = kmap_atomic(page, KM_USER0);
 193         cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
 194                         zram->table[index].offset;
 195
 196         memcpy(user_mem, cmem, PAGE_SIZE);
 197         kunmap_atomic(user_mem, KM_USER0);
 198         kunmap_atomic(cmem, KM_USER1);
 199
 200         flush_dcache_page(page);
 201 }
 202
 203 static int zram_read(struct zram *zram, struct bio *bio)
 204 {
 205
 206         int i;
 207         u32 index;
 208         struct bio_vec *bvec;
 209
 210         if (unlikely(!zram->init_done)) {
 211                 set_bit(BIO_UPTODATE, &bio->bi_flags);
 212                 bio_endio(bio, 0);
 213                 return 0;
 214         }
 215
 216         zram_stat64_inc(zram, &zram->stats.num_reads);
 217         index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
 218
 219         bio_for_each_segment(bvec, bio, i) {
 220                 int ret;
 221                 size_t clen;
 222                 struct page *page;
 223                 struct zobj_header *zheader;
 224                 unsigned char *user_mem, *cmem;
 225
 226                 page = bvec->bv_page;
 227
 228                 if (zram_test_flag(zram, index, ZRAM_ZERO)) {
 229                         handle_zero_page(page);
 230                         index++;
 231                         continue;
 232                 }
 233
 234                 /* Requested page is not present in compressed area */
 235                 if (unlikely(!zram->table[index].page)) {
 236                         pr_debug("Read before write: sector=%lu, size=%u",
 237                                 (ulong)(bio->bi_sector), bio->bi_size);
 238                         /* Do nothing */
 239                         index++;
 240                         continue;
 241                 }
 242
 243                 /* Page is stored uncompressed since it's incompressible */
 244                 if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED))) {
 245                         handle_uncompressed_page(zram, page, index);
 246                         index++;
 247                         continue;
 248                 }
 249
 250                 user_mem = kmap_atomic(page, KM_USER0);
 251                 clen = PAGE_SIZE;
 252
 253                 cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
 254                                 zram->table[index].offset;
 255
 256                 ret = lzo1x_decompress_safe(
 257                         cmem + sizeof(*zheader),
 258                         xv_get_object_size(cmem) - sizeof(*zheader),
 259                         user_mem, &clen);
 260
 261                 kunmap_atomic(user_mem, KM_USER0);
 262                 kunmap_atomic(cmem, KM_USER1);
 263
 264                 /* Should NEVER happen. Return bio error if it does. */
 265                 if (unlikely(ret != LZO_E_OK)) {
 266                         pr_err("Decompression failed! err=%d, page=%u\n",
 267                                 ret, index);
 268                         zram_stat64_inc(zram, &zram->stats.failed_reads);
 269                         goto out;
 270                 }
 271
 272                 flush_dcache_page(page);
 273                 index++;
 274         }
 275
 276         set_bit(BIO_UPTODATE, &bio->bi_flags);
 277         bio_endio(bio, 0);
 278         return 0;
 279
 280 out:
 281         bio_io_error(bio);
 282         return 0;
 283 }
 284
 285 static int zram_write(struct zram *zram, struct bio *bio)
 286 {
 287         int i, ret;
 288         u32 index;
 289         struct bio_vec *bvec;
 290
 291         if (unlikely(!zram->init_done)) {
 292                 ret = zram_init_device(zram);
 293                 if (ret)
 294                         goto out;
 295         }
 296
 297         zram_stat64_inc(zram, &zram->stats.num_writes);
 298         index = bio->bi_sector >> SECTORS_PER_PAGE_SHIFT;
 299
 300         bio_for_each_segment(bvec, bio, i) {
 301                 u32 offset;
 302                 size_t clen;
 303                 struct zobj_header *zheader;
 304                 struct page *page, *page_store;
 305                 unsigned char *user_mem, *cmem, *src;
 306
 307                 page = bvec->bv_page;
 308                 src = zram->compress_buffer;
 309
 310                 /*
 311                  * System overwrites unused sectors. Free memory associated
 312                  * with this sector now.
 313                  */
 314                 if (zram->table[index].page ||
 315                                 zram_test_flag(zram, index, ZRAM_ZERO))
 316                         zram_free_page(zram, index);
 317
 318                 mutex_lock(&zram->lock);
 319
 320                 user_mem = kmap_atomic(page, KM_USER0);
 321                 if (page_zero_filled(user_mem)) {
 322                         kunmap_atomic(user_mem, KM_USER0);
 323                         mutex_unlock(&zram->lock);
 324                         zram_stat_inc(&zram->stats.pages_zero);
 325                         zram_set_flag(zram, index, ZRAM_ZERO);
 326                         index++;
 327                         continue;
 328                 }
 329
 330                 ret = lzo1x_1_compress(user_mem, PAGE_SIZE, src, &clen,
 331                                         zram->compress_workmem);
 332
 333                 kunmap_atomic(user_mem, KM_USER0);
 334
 335                 if (unlikely(ret != LZO_E_OK)) {
 336                         mutex_unlock(&zram->lock);
 337                         pr_err("Compression failed! err=%d\n", ret);
 338                         zram_stat64_inc(zram, &zram->stats.failed_writes);
 339                         goto out;
 340                 }
 341
 342                 /*
 343                  * Page is incompressible. Store it as-is (uncompressed)
 344                  * since we do not want to return too many disk write
 345                  * errors which has side effect of hanging the system.
 346                  */
 347                 if (unlikely(clen > max_zpage_size)) {
 348                         clen = PAGE_SIZE;
 349                         page_store = alloc_page(GFP_NOIO | __GFP_HIGHMEM);
 350                         if (unlikely(!page_store)) {
 351                                 mutex_unlock(&zram->lock);
 352                                 pr_info("Error allocating memory for "
 353                                         "incompressible page: %u\n", index);
 354                                 zram_stat64_inc(zram,
 355                                         &zram->stats.failed_writes);
 356                                 goto out;
 357                         }
 358
 359                         offset = 0;
 360                         zram_set_flag(zram, index, ZRAM_UNCOMPRESSED);
 361                         zram_stat_inc(&zram->stats.pages_expand);
 362                         zram->table[index].page = page_store;
 363                         src = kmap_atomic(page, KM_USER0);
 364                         goto memstore;
 365                 }
 366
 367                 if (xv_malloc(zram->mem_pool, clen + sizeof(*zheader),
 368                                 &zram->table[index].page, &offset,
 369                                 GFP_NOIO | __GFP_HIGHMEM)) {
 370                         mutex_unlock(&zram->lock);
 371                         pr_info("Error allocating memory for compressed "
 372                                 "page: %u, size=%zu\n", index, clen);
 373                         zram_stat64_inc(zram, &zram->stats.failed_writes);
 374                         goto out;
 375                 }
 376
 377 memstore:
 378                 zram->table[index].offset = offset;
 379
 380                 cmem = kmap_atomic(zram->table[index].page, KM_USER1) +
 381                                 zram->table[index].offset;
 382
 383 #if 0
 384                 /* Back-reference needed for memory defragmentation */
 385                 if (!zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)) {
 386                         zheader = (struct zobj_header *)cmem;
 387                         zheader->table_idx = index;
 388                         cmem += sizeof(*zheader);
 389                 }
 390 #endif
 391
 392                 memcpy(cmem, src, clen);
 393
 394                 kunmap_atomic(cmem, KM_USER1);
 395                 if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)))
 396                         kunmap_atomic(src, KM_USER0);
 397
 398                 /* Update stats */
 399                 zram_stat64_add(zram, &zram->stats.compr_size, clen);
 400                 zram_stat_inc(&zram->stats.pages_stored);
 401                 if (clen <= PAGE_SIZE / 2)
 402                         zram_stat_inc(&zram->stats.good_compress);
 403
 404                 mutex_unlock(&zram->lock);
 405                 index++;
 406         }
 407
 408         set_bit(BIO_UPTODATE, &bio->bi_flags);
 409         bio_endio(bio, 0);
 410         return 0;
 411
 412 out:
 413         bio_io_error(bio);
 414         return 0;
 415 }
 416
 417 /*
 418  * Check if request is within bounds and page aligned.
 419  */
 420 static inline int valid_io_request(struct zram *zram, struct bio *bio)
 421 {
 422         if (unlikely(
 423                 (bio->bi_sector >= (zram->disksize >> SECTOR_SHIFT)) ||
 424                 (bio->bi_sector & (SECTORS_PER_PAGE - 1)) ||
 425                 (bio->bi_size & (PAGE_SIZE - 1)))) {
 426
 427                 return 0;
 428         }
 429
 430         /* I/O request is valid */
 431         return 1;
 432 }
 433
 434 /*
 435  * Handler function for all zram I/O requests.
 436  */
 437 static int zram_make_request(struct request_queue *queue, struct bio *bio)
 438 {
 439         int ret = 0;
 440         struct zram *zram = queue->queuedata;
 441
 442         if (!valid_io_request(zram, bio)) {
 443                 zram_stat64_inc(zram, &zram->stats.invalid_io);
 444                 bio_io_error(bio);
 445                 return 0;
 446         }
 447
 448         switch (bio_data_dir(bio)) {
 449         case READ:
 450                 ret = zram_read(zram, bio);
 451                 break;
 452
 453         case WRITE:
 454                 ret = zram_write(zram, bio);
 455                 break;
 456         }
 457
 458         return ret;
 459 }
 460
 461 void zram_reset_device(struct zram *zram)
 462 {
 463         size_t index;
 464
 465         mutex_lock(&zram->init_lock);
 466         zram->init_done = 0;
 467
 468         /* Free various per-device buffers */
 469         kfree(zram->compress_workmem);
 470         free_pages((unsigned long)zram->compress_buffer, 1);
 471
 472         zram->compress_workmem = NULL;
 473         zram->compress_buffer = NULL;
 474
 475         /* Free all pages that are still in this zram device */
 476         for (index = 0; index < zram->disksize >> PAGE_SHIFT; index++) {
 477                 struct page *page;
 478                 u16 offset;
 479
 480                 page = zram->table[index].page;
 481                 offset = zram->table[index].offset;
 482
 483                 if (!page)
 484                         continue;
 485
 486                 if (unlikely(zram_test_flag(zram, index, ZRAM_UNCOMPRESSED)))
 487                         __free_page(page);
 488                 else
 489                         xv_free(zram->mem_pool, page, offset);
 490         }
 491
 492         vfree(zram->table);
 493         zram->table = NULL;
 494
 495         xv_destroy_pool(zram->mem_pool);
 496         zram->mem_pool = NULL;
 497
 498         /* Reset stats */
 499         memset(&zram->stats, 0, sizeof(zram->stats));
 500
 501         zram->disksize = 0;
 502         mutex_unlock(&zram->init_lock);
 503 }
 504
 505 int zram_init_device(struct zram *zram)
 506 {
 507         int ret;
 508         size_t num_pages;
 509
 510         mutex_lock(&zram->init_lock);
 511
 512         if (zram->init_done) {
 513                 mutex_unlock(&zram->init_lock);
 514                 return 0;
 515         }
 516
 517         zram_set_disksize(zram, totalram_pages << PAGE_SHIFT);
 518
 519         zram->compress_workmem = kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
 520         if (!zram->compress_workmem) {
 521                 pr_err("Error allocating compressor working memory!\n");
 522                 ret = -ENOMEM;
 523                 goto fail;
 524         }
 525
 526         zram->compress_buffer = (void *)__get_free_pages(__GFP_ZERO, 1);
 527         if (!zram->compress_buffer) {
 528                 pr_err("Error allocating compressor buffer space\n");
 529                 ret = -ENOMEM;
 530                 goto fail;
 531         }
 532
 533         num_pages = zram->disksize >> PAGE_SHIFT;
 534         zram->table = vzalloc(num_pages * sizeof(*zram->table));
 535         if (!zram->table) {
 536                 pr_err("Error allocating zram address table\n");
 537                 /* To prevent accessing table entries during cleanup */
 538                 zram->disksize = 0;
 539                 ret = -ENOMEM;
 540                 goto fail;
 541         }
 542
 543         set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
 544
 545         /* zram devices sort of resembles non-rotational disks */
 546         queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
 547
 548         zram->mem_pool = xv_create_pool();
 549         if (!zram->mem_pool) {
 550                 pr_err("Error creating memory pool\n");
 551                 ret = -ENOMEM;
 552                 goto fail;
 553         }
 554
 555         zram->init_done = 1;
 556         mutex_unlock(&zram->init_lock);
 557
 558         pr_debug("Initialization done!\n");
 559         return 0;
 560
 561 fail:
 562         mutex_unlock(&zram->init_lock);
 563         zram_reset_device(zram);
 564
 565         pr_err("Initialization failed: err=%d\n", ret);
 566         return ret;
 567 }
 568
 569 void zram_slot_free_notify(struct block_device *bdev, unsigned long index)
 570 {
 571         struct zram *zram;
 572
 573         zram = bdev->bd_disk->private_data;
 574         zram_free_page(zram, index);
 575         zram_stat64_inc(zram, &zram->stats.notify_free);
 576 }
 577
 578 static const struct block_device_operations zram_devops = {
 579         .swap_slot_free_notify = zram_slot_free_notify,
 580         .owner = THIS_MODULE
 581 };
 582
 583 static int create_device(struct zram *zram, int device_id)
 584 {
 585         int ret = 0;
 586
 587         mutex_init(&zram->lock);
 588         mutex_init(&zram->init_lock);
 589         spin_lock_init(&zram->stat64_lock);
 590
 591         zram->queue = blk_alloc_queue(GFP_KERNEL);
 592         if (!zram->queue) {
 593                 pr_err("Error allocating disk queue for device %d\n",
 594                         device_id);
 595                 ret = -ENOMEM;
 596                 goto out;
 597         }
 598
 599         blk_queue_make_request(zram->queue, zram_make_request);
 600         zram->queue->queuedata = zram;
 601
 602          /* gendisk structure */
 603         zram->disk = alloc_disk(1);
 604         if (!zram->disk) {
 605                 blk_cleanup_queue(zram->queue);
 606                 pr_warning("Error allocating disk structure for device %d\n",
 607                         device_id);
 608                 ret = -ENOMEM;
 609                 goto out;
 610         }
 611
 612         zram->disk->major = zram_major;
 613         zram->disk->first_minor = device_id;
 614         zram->disk->fops = &zram_devops;
 615         zram->disk->queue = zram->queue;
 616         zram->disk->private_data = zram;
 617         snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
 618
 619         /* Actual capacity set using syfs (/sys/block/zram<id>/disksize */
 620         set_capacity(zram->disk, 0);
 621
 622         /*
 623          * To ensure that we always get PAGE_SIZE aligned
 624          * and n*PAGE_SIZED sized I/O requests.
 625          */
 626         blk_queue_physical_block_size(zram->disk->queue, PAGE_SIZE);
 627         blk_queue_logical_block_size(zram->disk->queue, PAGE_SIZE);
 628         blk_queue_io_min(zram->disk->queue, PAGE_SIZE);
 629         blk_queue_io_opt(zram->disk->queue, PAGE_SIZE);
 630
 631         add_disk(zram->disk);
 632
 633 #ifdef CONFIG_SYSFS
 634         ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,
 635                                 &zram_disk_attr_group);
 636         if (ret < 0) {
 637                 pr_warning("Error creating sysfs group");
 638                 goto out;
 639         }
 640 #endif
 641
 642         zram->init_done = 0;
 643
 644 out:
 645         return ret;
 646 }
 647
 648 static void destroy_device(struct zram *zram)
 649 {
 650 #ifdef CONFIG_SYSFS
 651         sysfs_remove_group(&disk_to_dev(zram->disk)->kobj,
 652                         &zram_disk_attr_group);
 653 #endif
 654
 655         if (zram->disk) {
 656                 del_gendisk(zram->disk);
 657                 put_disk(zram->disk);
 658         }
 659
 660         if (zram->queue)
 661                 blk_cleanup_queue(zram->queue);
 662 }
 663
 664 static int __init zram_init(void)
 665 {
 666         int ret, dev_id;
 667
 668         if (num_devices > max_num_devices) {
 669                 pr_warning("Invalid value for num_devices: %u\n",
 670                                 num_devices);
 671                 ret = -EINVAL;
 672                 goto out;
 673         }
 674
 675         zram_major = register_blkdev(0, "zram");
 676         if (zram_major <= 0) {
 677                 pr_warning("Unable to get major number\n");
 678                 ret = -EBUSY;
 679                 goto out;
 680         }
 681
 682         if (!num_devices) {
 683                 pr_info("num_devices not specified. Using default: 1\n");
 684                 num_devices = 1;
 685         }
 686
 687         /* Allocate the device array and initialize each one */
 688         pr_info("Creating %u devices ...\n", num_devices);
 689         devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL);
 690         if (!devices) {
 691                 ret = -ENOMEM;
 692                 goto unregister;
 693         }
 694
 695         for (dev_id = 0; dev_id < num_devices; dev_id++) {
 696                 ret = create_device(&devices[dev_id], dev_id);
 697                 if (ret)
 698                         goto free_devices;
 699         }
 700
 701         return 0;
 702
 703 free_devices:
 704         while (dev_id)
 705                 destroy_device(&devices[--dev_id]);
 706         kfree(devices);
 707 unregister:
 708         unregister_blkdev(zram_major, "zram");
 709 out:
 710         return ret;
 711 }
 712
 713 static void __exit zram_exit(void)
 714 {
 715         int i;
 716         struct zram *zram;
 717
 718         for (i = 0; i < num_devices; i++) {
 719                 zram = &devices[i];
 720
 721                 destroy_device(zram);
 722                 if (zram->init_done)
 723                         zram_reset_device(zram);
 724         }
 725
 726         unregister_blkdev(zram_major, "zram");
 727
 728         kfree(devices);
 729         pr_debug("Cleanup done!\n");
 730 }
 731
 732 module_param(num_devices, uint, 0);
 733 MODULE_PARM_DESC(num_devices, "Number of zram devices");
 734
 735 module_init(zram_init);
 736 module_exit(zram_exit);
 737
 738 MODULE_LICENSE("Dual BSD/GPL");
 739 MODULE_AUTHOR("Nitin Gupta <ngupta@vflare.org>");
 740 MODULE_DESCRIPTION("Compressed RAM Block Device");